Generally, baker's yeast is obtained from a culture medium consisting either of sugar molasses and chemical additives, or of cereals. However, said culture mediums necessitate a separation between the medium and the microorganism after the growth of the latter, in order to obtain a sufficient concentration of microorganisms permitting a panification under conditions which are compatible with an industrial production.
In the case of a so called "sour dough" panification, the production of the sponge necessitates successive pre-cultures and a long adaptation of the microorganisms to the cereal environment, which both are incompatible with an industrial production.